Following steps in first post of this thread, created a dsdt.aml using layout-id 3. Installed with Multibeast, using only the UserDSDT setting. Have not installed any audio drivers from Multibeast.
I did not install a patched AppleHDA because of this section from the first post:
New "Feature" of Mountain Lion AppleHDA
1. AMD/Nvidia and HD3000/HD4000 HDMI audio works without on board audio working (assuming dsdt edits) by setting HDEF/layout_id to an existing Apple layout_id such as 1. That means systems with mea can have HDMI audio and AirPlay audio using the native AppleHDA.kext in Mountain Lion (do not Install a Patched AppleHDA for this feature).